4/23/2012. Program development to Preliminary Design level by the Biosolids Program Manager. Thermal hydrolysis/digestion challenges and innovations

Transcription

1 Perry Schafer, PE, BCEE, Brown and Caldwell DC Water Biosolids Management Team Program development to Preliminary Design level by the Biosolids Program Manager Thermal hydrolysis/digestion challenges and innovations April 25, 212 Procurement issues for TH/digestion at Blue Plains Existing Solids Processing Area - Class B Lime Stabilization New Biosolids Program Site (7 acres) System and Peaking 212-Existing Lime Stabilization Average Annual 34 Peak Month 4-45 Peak Week and Greater 4-45 * TH- Average Annual Peak Month Peak Week and Greater * Higher production peaks are stored within existing processes. 215-New System Backup Backup Up to

2 Gravity Thickeners Blend Tank DAFTs Screening and Pre- Power Steam Emissions Cambi THP Lime Biogas Treatment and CHP Mix Biogas Anaerobic Store & Final ecycle Processing Class A Cake product will be ~3 % solids, stable, screened, Class A The Plan: Continued land applicationinitial focus Develop and maximize marketable products starting in 215 Further processing likely, including blending materials with Class A cake Under Chris Peot s leadership at DC Water TH/digested cake land application at Aberdeen, Scotland Class B 5 6 Feeding ~1% Solids Ft 3 biogas/day Ft 3 of tankage DC Water Digesters Typical Sludge VS loading at.4 + lb VS/ft 3 /day Only 15 MG of Digesters, ather than 4+MG required for typical MAD At $5/gal = $125+ million savings and much less space required Taller tanks for capacity, mixing, and saves space Optional concrete construction methods for price competition DC Water tanks are 3.8 MG each (~95ft Ø by 7 + ft SWD) Gas Takeoff Motor Tank Headspace Typical Draft Tube Mixing System 5 per Tank Backup and Emergency Overflows Continuous Normal Surface Overflow Continuous Bottom Withdrawal 2

3 Four Cambi THP Trains Typically 8-9 C Thermally Hydrolyzed Solids Higher pressure portion of feed loop Cooling HEXs Digesters Documented events of rapid liquid level rise (gas holdup) Highly-loaded, tall digesters with thick solids increase the risk Control measures include continuous feed, controlled DTM mixing, extra freeboard, huge overflow capacity, and overflow storage Overpressure damaged fixed cover digester = Control Valve with Flow Meter Cake Bin Pre- Centrifuges 15 to 18% Solids Cake drops directly into cake bins Pre-dewatered cake pumped minimum distance to THP trains Final (BFP) cake-single belt conveyor to loadout PC Pump to Cambi THP Detailed business case evaluation of BFPs vs. centrifuges Both technologies achieve ~3% solids BFPs use less energy Net present value of options was similar - space requirements also similar No regrowth with either, but odor regrowth potential with centrifuge BFP pilot testing in U.K. on Cambi/digested feed to determine parameters for design Cake Cake Solids Solids (%) Belt Filter Filter Press Press Centrifuge THP THP Site 3

4 Maximize power production and meet steam needs of Cambi THP 12 bar (175 psi) steam 73 % overall power/heat efficiency Low-NO x emissions from Solar Mercury 5 gas turbine Flexible operation to meet peak steam needs 3 Turbine/HSG system is being installed: ~13 MW total power, ~1 MW net power Exhaust Gas HSG Steam to Cambi THP Duct Burner Digester Gas Turbine Gas Compressor Generator Power to Gas (Solar Mercury 5) Blue Plains AWTP Supplemental Natural Gas Combustion Air Single point responsibility for design and construction Schedule advantages Ability to share risks appropriately Earlier price determination Tunnel project decision was already made-db TH projects typically procured overseas via DB DB A decade of TH evaluation, site visits and &D work, resulted in sole-source decision in 29 Determined that Cambi s THP was the only TH system proven at the scale required for Blue Plains DC Water then contracted with Cambi to define the interfaces for Blue Plains Cambi THP 4 Train System for DC Water 16 4

5 Screening and Pre- Main Process Train Prescriptive FP to insure facilities will fit and Cambi THP provide high-quality equipment/system Workshops to assess risks Market surveys of potential DB contractors Discussions with TH owners in UK/Europe Examined experience of other large vendor systems within major project procurement Conclusion: DC Water/Program Management developed Term Sheet for Cambi THP (scope/price/key terms established). Term Sheet expanded to Cambi subcontract by winning DB Team Screening and Pre- Main Process Train Cambi THP For critical equipment, specific vendors were named Over 3 Performance Guarantees/Acceptance Tests were defined: capacity, performance, permit-related Limited Technical Alternatives were allowed within the proposal process 6 SOQs received, then short-listed to 3 for proposals with price/technical evaluation. Successful DB procurement process 17 Gravity Thickeners Blend Tank DAFTs Screening and Pre- Power Steam Emissions Lime Biogas Treatment and CHP Cambi THP Mix DB DBO Biogas Anaerobic Store & Final ecycle Processing DBB Site Preparation DBB Class A Class B 19 5

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